Can we suggest coming down to a specific head unit? I'll take your guidance on this. I want to spend about $300 - $350 - or $400 without installing costs. And I want the unit to be able to play videos. Any format.
Sorry, have come back a bit late on this as I simply missed it. Maybe this is all in vain but here goes anyway.
I don't know of any reputable H/U that sells in this range WITH good integration into the current vehicle. If that is not important then there are plenty of units out there. I'd suggest ringing a car audio specialist and explaining your budget. They might be able to come up with a solution that is closer to your budget. Always ask the questions I mentioned before so you are well-aware of what you are getting/expecting and what you are not (getting).
It's nigh impossible to pinpoint a specific head unit for you because there are many 'stand-alone' head units available that would do the job. You have to be clearer on what you want. I'll take you through the process I took:
I wanted a head unit to replace my original GM one as I got frustrated with a simple 'Audio' input and 6-stacker CD. I wanted to play music from both my phone and my partner's phone as a minimum. My BT (hands free calls) just did not work any more. Holden had looked at the entire system multiple times and effectively gave up. I gave up my overhead DVD player as it was on its last legs, and my kids are no longer 'kids' (therefore I needed no integration with this, but I could have got integration with a new Alpine DVD if needed - I didn't - but can always upgrade later anyway).
I did NOT want a 'dumb' unit. I wanted integration with my current steering wheel controls, and I wanted integration with my HVAC. [Note: I could have gone with a different brand HVAC setup but decided I wanted it all the same - my choice].
I also wanted a reverse camera. I did NOT (at the time) require my speakers to be replaced, I was happy with stock standard ones (I have since replaced them because of water leaks/corrosion problems since fixed).
Generally, I wanted the new H/U to 'work' with my current vehicle. I really like steering wheel controls (especially for long trips) for basic functions. I wanted a DAB radio and Apple/CarPlay/Android but could have done without about 40% of the extra functionality it comes with (easy, don't use it). If integration is not important to you, then it will be MUCH cheaper.
Another note: Me calling 'stand-alone' head units 'dumb' is simply that they don't integrate with the current vehicle make/model controls. There are people who do NOT want integration - for a few very valid reasons. They want a stand-alone system and they pay for the build-quality/sound/ease-of-use/features etc, but NOT for specific vehicle integration. This is entirely valid. You have to know what you want, and go find it.
I knew what I wanted (and didn't) and contacted a few specialists - and also researched online. I picked a place and they both supplied and fitted it. I did think about fitting it myself but decided if i'm going to pay for a reasonable unit (and the thought of integration) then I might as well not skimp on fitting. I'm glad I got it fitted with hind sight.
You've already specified a requirement to play vids. That's good. Now think about the rest of your requirements.
You - Short-sighted, age/disability-related issues? (human interface to unit)
Vehicle - Berlina. What's my car got, what does it need. What can I leverage off?
HVAC integration - important? Does my HVAC work correctly now?
Speakers - replacement? Currently OK, or want different sound? Do you need to do extra with VE doors? What's the cost $$$?
Min unit functionality? Software/ Hardware.
DAB (and others)? Do I need better antenna? Will stock H/U ant be OK?
Future requirements? Any? AKA - I don't need this now, but might/will in the future...
Cheers